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<a href="clock__type__fwd_8hpp.html">Go to the documentation of this file.</a><div class="fragment"><div class="line"><a id="l00001" name="l00001"></a><span class="lineno">    1</span><span class="comment">/* Flow</span></div>
<div class="line"><a id="l00002" name="l00002"></a><span class="lineno">    2</span><span class="comment"> * Copyright 2023 Akamai Technologies, Inc.</span></div>
<div class="line"><a id="l00003" name="l00003"></a><span class="lineno">    3</span><span class="comment"> *</span></div>
<div class="line"><a id="l00004" name="l00004"></a><span class="lineno">    4</span><span class="comment"> * Licensed under the Apache License, Version 2.0 (the</span></div>
<div class="line"><a id="l00005" name="l00005"></a><span class="lineno">    5</span><span class="comment"> * &quot;License&quot;); you may not use this file except in</span></div>
<div class="line"><a id="l00006" name="l00006"></a><span class="lineno">    6</span><span class="comment"> * compliance with the License.  You may obtain a copy</span></div>
<div class="line"><a id="l00007" name="l00007"></a><span class="lineno">    7</span><span class="comment"> * of the License at</span></div>
<div class="line"><a id="l00008" name="l00008"></a><span class="lineno">    8</span><span class="comment"> *</span></div>
<div class="line"><a id="l00009" name="l00009"></a><span class="lineno">    9</span><span class="comment"> *   https://www.apache.org/licenses/LICENSE-2.0</span></div>
<div class="line"><a id="l00010" name="l00010"></a><span class="lineno">   10</span><span class="comment"> *</span></div>
<div class="line"><a id="l00011" name="l00011"></a><span class="lineno">   11</span><span class="comment"> * Unless required by applicable law or agreed to in</span></div>
<div class="line"><a id="l00012" name="l00012"></a><span class="lineno">   12</span><span class="comment"> * writing, software distributed under the License is</span></div>
<div class="line"><a id="l00013" name="l00013"></a><span class="lineno">   13</span><span class="comment"> * distributed on an &quot;AS IS&quot; BASIS, WITHOUT WARRANTIES OR</span></div>
<div class="line"><a id="l00014" name="l00014"></a><span class="lineno">   14</span><span class="comment"> * CONDITIONS OF ANY KIND, either express or implied.</span></div>
<div class="line"><a id="l00015" name="l00015"></a><span class="lineno">   15</span><span class="comment"> * See the License for the specific language governing</span></div>
<div class="line"><a id="l00016" name="l00016"></a><span class="lineno">   16</span><span class="comment"> * permissions and limitations under the License. */</span></div>
<div class="line"><a id="l00017" name="l00017"></a><span class="lineno">   17</span><span class="comment"></span> </div>
<div class="line"><a id="l00018" name="l00018"></a><span class="lineno">   18</span><span class="comment">/// @file</span></div>
<div class="line"><a id="l00019" name="l00019"></a><span class="lineno">   19</span><span class="comment"></span><span class="preprocessor">#pragma once</span></div>
<div class="line"><a id="l00020" name="l00020"></a><span class="lineno">   20</span> </div>
<div class="line"><a id="l00021" name="l00021"></a><span class="lineno">   21</span><span class="preprocessor">#include &quot;<a class="code" href="common_8hpp.html">flow/common.hpp</a>&quot;</span></div>
<div class="line"><a id="l00022" name="l00022"></a><span class="lineno">   22</span><span class="preprocessor">#include &lt;bitset&gt;</span></div>
<div class="line"><a id="l00023" name="l00023"></a><span class="lineno">   23</span><span class="preprocessor">#include &lt;ostream&gt;</span></div>
<div class="line"><a id="l00024" name="l00024"></a><span class="lineno">   24</span> </div>
<div class="line"><a id="l00025" name="l00025"></a><span class="lineno">   25</span><span class="keyword">namespace </span><a class="code hl_namespace" href="namespaceflow_1_1perf.html">flow::perf</a></div>
<div class="line"><a id="l00026" name="l00026"></a><span class="lineno">   26</span>{</div>
<div class="line"><a id="l00027" name="l00027"></a><span class="lineno">   27</span><span class="comment">// Types.</span></div>
<div class="line"><a id="l00028" name="l00028"></a><span class="lineno">   28</span><span class="comment"></span> </div>
<div class="line"><a id="l00029" name="l00029"></a><span class="lineno">   29</span><span class="comment">/**</span></div>
<div class="line"><a id="l00030" name="l00030"></a><span class="lineno">   30</span><span class="comment"> * Short-hand for a high-precision boost.chrono point in time, formally equivalent to flow::Fine_time_pt.</span></div>
<div class="line"><a id="l00031" name="l00031"></a><span class="lineno">   31</span><span class="comment"> * The alias exists 1/2 for brevity, 1/2 to declare the standardly-used time point type in flow::perf Flow module.</span></div>
<div class="line"><a id="l00032" name="l00032"></a><span class="lineno">   32</span><span class="comment"> */</span></div>
<div class="line"><a id="l00033" name="l00033"></a><span class="lineno"><a class="line" href="namespaceflow_1_1perf.html#ace5f154155a7d9d5c112c1a83aa04fb5">   33</a></span><span class="keyword">using </span><a class="code hl_typedef" href="namespaceflow_1_1perf.html#ace5f154155a7d9d5c112c1a83aa04fb5">Time_pt</a> = <a class="code hl_typedef" href="namespaceflow.html#a9d9cc2eeb10d398cff5591d446b763b8">Fine_time_pt</a>;</div>
<div class="line"><a id="l00034" name="l00034"></a><span class="lineno">   34</span><span class="comment"></span> </div>
<div class="line"><a id="l00035" name="l00035"></a><span class="lineno">   35</span><span class="comment">/**</span></div>
<div class="line"><a id="l00036" name="l00036"></a><span class="lineno">   36</span><span class="comment"> * Short-hand for a high-precision boost.chrono duration, formally equivalent to flow::Fine_duration.</span></div>
<div class="line"><a id="l00037" name="l00037"></a><span class="lineno">   37</span><span class="comment"> * The alias exists 1/2 for brevity, 1/2 to declare the standardly-used duration type in flow::perf Flow module.</span></div>
<div class="line"><a id="l00038" name="l00038"></a><span class="lineno">   38</span><span class="comment"> */</span></div>
<div class="line"><a id="l00039" name="l00039"></a><span class="lineno"><a class="line" href="namespaceflow_1_1perf.html#a38e42ae0923eb23052e3a8a1e7956456">   39</a></span><span class="keyword">using </span><a class="code hl_typedef" href="namespaceflow_1_1perf.html#a38e42ae0923eb23052e3a8a1e7956456">Duration</a> = <a class="code hl_typedef" href="namespaceflow.html#a48799f1263cdeedec125be51a3db2b79">Fine_duration</a>;</div>
<div class="line"><a id="l00040" name="l00040"></a><span class="lineno">   40</span><span class="comment"></span> </div>
<div class="line"><a id="l00041" name="l00041"></a><span class="lineno">   41</span><span class="comment">/**</span></div>
<div class="line"><a id="l00042" name="l00042"></a><span class="lineno">   42</span><span class="comment"> * The raw type used in #Duration to store its clock ticks.  It is likely `int64_t`, but try not to rely on that</span></div>
<div class="line"><a id="l00043" name="l00043"></a><span class="lineno">   43</span><span class="comment"> * directly.</span></div>
<div class="line"><a id="l00044" name="l00044"></a><span class="lineno">   44</span><span class="comment"> *</span></div>
<div class="line"><a id="l00045" name="l00045"></a><span class="lineno">   45</span><span class="comment"> * ### Rationale ###</span></div>
<div class="line"><a id="l00046" name="l00046"></a><span class="lineno">   46</span><span class="comment"> * Useful, e.g., in `atomic&lt;duration_rep_t&gt;`, when one wants to perform high-performance operations like</span></div>
<div class="line"><a id="l00047" name="l00047"></a><span class="lineno">   47</span><span class="comment"> * `+=` and `fetch_add()` on `atomic&lt;&gt;`s: these do not exist for `chrono::duration`, because the latter is not an</span></div>
<div class="line"><a id="l00048" name="l00048"></a><span class="lineno">   48</span><span class="comment"> * integral type.</span></div>
<div class="line"><a id="l00049" name="l00049"></a><span class="lineno">   49</span><span class="comment"> */</span></div>
<div class="line"><a id="l00050" name="l00050"></a><span class="lineno"><a class="line" href="namespaceflow_1_1perf.html#a75b06c669e720c60621f3c68c3d34408">   50</a></span><span class="keyword">using </span><a class="code hl_typedef" href="namespaceflow_1_1perf.html#a75b06c669e720c60621f3c68c3d34408">duration_rep_t</a> = Duration::rep;</div>
<div class="line"><a id="l00051" name="l00051"></a><span class="lineno">   51</span><span class="comment"></span> </div>
<div class="line"><a id="l00052" name="l00052"></a><span class="lineno">   52</span><span class="comment">/**</span></div>
<div class="line"><a id="l00053" name="l00053"></a><span class="lineno">   53</span><span class="comment"> * Clock types supported by flow::perf module facilities, perf::Checkpointing_timer in particular.</span></div>
<div class="line"><a id="l00054" name="l00054"></a><span class="lineno">   54</span><span class="comment"> * These are used, among other things, as array/`vector` indices and therefore numerically equal 0, 1, ....</span></div>
<div class="line"><a id="l00055" name="l00055"></a><span class="lineno">   55</span><span class="comment"> * Clock_type::S_END_SENTINEL is an invalid clock type whose numerical value equals the number of clock types</span></div>
<div class="line"><a id="l00056" name="l00056"></a><span class="lineno">   56</span><span class="comment"> * available.</span></div>
<div class="line"><a id="l00057" name="l00057"></a><span class="lineno">   57</span><span class="comment"> *</span></div>
<div class="line"><a id="l00058" name="l00058"></a><span class="lineno">   58</span><span class="comment"> * @todo Consider adding a system-calendar-clock (a/k/a POSIX time) type to perf::Clock_type.  It would be a cousin</span></div>
<div class="line"><a id="l00059" name="l00059"></a><span class="lineno">   59</span><span class="comment"> * of Clock_type::S_REAL_HI_RES.  It would certainly be inferior in terms of resolution/monotonicity/etc., and one would</span></div>
<div class="line"><a id="l00060" name="l00060"></a><span class="lineno">   60</span><span class="comment"> * think `S_REAL_HI_RES` would always be preferable.  Nevertheless it would be interesting to &quot;officially&quot; see its</span></div>
<div class="line"><a id="l00061" name="l00061"></a><span class="lineno">   61</span><span class="comment"> * characteristics including in particular (1) resolution and (2) its own perf cost especially vs. `S_REAL_HI_RES` which</span></div>
<div class="line"><a id="l00062" name="l00062"></a><span class="lineno">   62</span><span class="comment"> * we know is quite fast itself.  This may also help a certain to-do listed as of this writing in the doc header</span></div>
<div class="line"><a id="l00063" name="l00063"></a><span class="lineno">   63</span><span class="comment"> * of flow::log FLOW_LOG_WITHOUT_CHECKING() (the main worker bee of the log system, the one that generates each log</span></div>
<div class="line"><a id="l00064" name="l00064"></a><span class="lineno">   64</span><span class="comment"> * time stamp).</span></div>
<div class="line"><a id="l00065" name="l00065"></a><span class="lineno">   65</span><span class="comment"> */</span></div>
<div class="line"><a id="l00066" name="l00066"></a><span class="lineno"><a class="line" href="namespaceflow_1_1perf.html#ad61fb186191e4bb824d14601d11a2eb0">   66</a></span><span class="keyword">enum class</span> <a class="code hl_enumeration" href="namespaceflow_1_1perf.html#ad61fb186191e4bb824d14601d11a2eb0">Clock_type</a> : <span class="keywordtype">size_t</span></div>
<div class="line"><a id="l00067" name="l00067"></a><span class="lineno">   67</span>{<span class="comment"></span></div>
<div class="line"><a id="l00068" name="l00068"></a><span class="lineno">   68</span><span class="comment">  /**</span></div>
<div class="line"><a id="l00069" name="l00069"></a><span class="lineno">   69</span><span class="comment">   * Measures real time (not processor time), using the highest-resolution system clock available that guarantees</span></div>
<div class="line"><a id="l00070" name="l00070"></a><span class="lineno">   70</span><span class="comment">   * steady, monotonic time passage with no discontinuities.  In POSIX `&quot;::clock_gettime(CLOCK_MONOTONIC)&quot;` is the</span></div>
<div class="line"><a id="l00071" name="l00071"></a><span class="lineno">   71</span><span class="comment">   * underlying native mechanism as of this writing.</span></div>
<div class="line"><a id="l00072" name="l00072"></a><span class="lineno">   72</span><span class="comment">   *</span></div>
<div class="line"><a id="l00073" name="l00073"></a><span class="lineno">   73</span><span class="comment">   * ### Obervations, informal suggestions ###</span></div>
<div class="line"><a id="l00074" name="l00074"></a><span class="lineno">   74</span><span class="comment">   * Of all clocks observed so far, it has the best resolution</span></div>
<div class="line"><a id="l00075" name="l00075"></a><span class="lineno">   75</span><span class="comment">   * and also is the cheapest computationally itself.  However, it measures real time, so (for example) another</span></div>
<div class="line"><a id="l00076" name="l00076"></a><span class="lineno">   76</span><span class="comment">   * thread or process pegging the processor concurrently can affect the time being measured.  That, in particular,</span></div>
<div class="line"><a id="l00077" name="l00077"></a><span class="lineno">   77</span><span class="comment">   * is not necessarily a problem in test rigs; but even so it cannot measure (for example) how costly one thread</span></div>
<div class="line"><a id="l00078" name="l00078"></a><span class="lineno">   78</span><span class="comment">   * is over another; nor does it separate idle time from computing time from I/O time from....</span></div>
<div class="line"><a id="l00079" name="l00079"></a><span class="lineno">   79</span><span class="comment">   *</span></div>
<div class="line"><a id="l00080" name="l00080"></a><span class="lineno">   80</span><span class="comment">   * Due to the high resolution and low computational cost, one should strive to use this clock whenever possible;</span></div>
<div class="line"><a id="l00081" name="l00081"></a><span class="lineno">   81</span><span class="comment">   * but it is not always possible (as additional info may be required, as outlined just above).</span></div>
<div class="line"><a id="l00082" name="l00082"></a><span class="lineno">   82</span><span class="comment">   */</span></div>
<div class="line"><a id="l00083" name="l00083"></a><span class="lineno">   83</span>  <a class="code hl_enumvalue" href="namespaceflow_1_1perf.html#ad61fb186191e4bb824d14601d11a2eb0a8cbf506eda585c026dfb5b72c402d342">S_REAL_HI_RES</a> = 0,</div>
<div class="line"><a id="l00084" name="l00084"></a><span class="lineno">   84</span><span class="comment"></span> </div>
<div class="line"><a id="l00085" name="l00085"></a><span class="lineno">   85</span><span class="comment">  /**</span></div>
<div class="line"><a id="l00086" name="l00086"></a><span class="lineno">   86</span><span class="comment">   * Along with `S_CPU_SYS_LO_RES`, measures processor time (user-level) spent by the current *process*;</span></div>
<div class="line"><a id="l00087" name="l00087"></a><span class="lineno">   87</span><span class="comment">   * this is the lower-resolution timer facility as in the `time` POSIX command.  In POSIX `&quot;::times()&quot;` is the</span></div>
<div class="line"><a id="l00088" name="l00088"></a><span class="lineno">   88</span><span class="comment">   * underlying native mechanism as of this writing.</span></div>
<div class="line"><a id="l00089" name="l00089"></a><span class="lineno">   89</span><span class="comment">   *</span></div>
<div class="line"><a id="l00090" name="l00090"></a><span class="lineno">   90</span><span class="comment">   * ### Obervations, informal suggestions ###</span></div>
<div class="line"><a id="l00091" name="l00091"></a><span class="lineno">   91</span><span class="comment">   * `S_CPU_TOTAL_HI_RES` is the superior processor-time clock; we have observed it to be equally computationally</span></div>
<div class="line"><a id="l00092" name="l00092"></a><span class="lineno">   92</span><span class="comment">   * expensive but delivering higher-resolution results.  However, it doesn&#39;t provide the classic user-kernel</span></div>
<div class="line"><a id="l00093" name="l00093"></a><span class="lineno">   93</span><span class="comment">   * split the way `S_CPU_SYS_LO_RES` and `S_CPU_USER_LO_RES` do together.</span></div>
<div class="line"><a id="l00094" name="l00094"></a><span class="lineno">   94</span><span class="comment">   *</span></div>
<div class="line"><a id="l00095" name="l00095"></a><span class="lineno">   95</span><span class="comment">   * See discussion on `S_CPU_TOTAL_HI_RES` regarding when/if to use process-time clocks.</span></div>
<div class="line"><a id="l00096" name="l00096"></a><span class="lineno">   96</span><span class="comment">   */</span></div>
<div class="line"><a id="l00097" name="l00097"></a><span class="lineno">   97</span>  <a class="code hl_enumvalue" href="namespaceflow_1_1perf.html#ad61fb186191e4bb824d14601d11a2eb0ae06b569eb44aff6a567186f4eddb12ed">S_CPU_USER_LO_RES</a>,</div>
<div class="line"><a id="l00098" name="l00098"></a><span class="lineno">   98</span><span class="comment"></span> </div>
<div class="line"><a id="l00099" name="l00099"></a><span class="lineno">   99</span><span class="comment">  /// Counterpart of `S_CPU_USER_LO_RES`, measuring processor time (kernel-level) spent by the current *process*.</span></div>
<div class="line"><a id="l00100" name="l00100"></a><span class="lineno">  100</span><span class="comment"></span>  <a class="code hl_enumvalue" href="namespaceflow_1_1perf.html#ad61fb186191e4bb824d14601d11a2eb0a1490431155a134162390180995550ca7">S_CPU_SYS_LO_RES</a>,</div>
<div class="line"><a id="l00101" name="l00101"></a><span class="lineno">  101</span><span class="comment"></span> </div>
<div class="line"><a id="l00102" name="l00102"></a><span class="lineno">  102</span><span class="comment">  /**</span></div>
<div class="line"><a id="l00103" name="l00103"></a><span class="lineno">  103</span><span class="comment">   * Measures processor time (user- and kernel-level total) spent by the current *process*;</span></div>
<div class="line"><a id="l00104" name="l00104"></a><span class="lineno">  104</span><span class="comment">   * this is the higher-resolution process-time facility.  In POSIX `&quot;::clock_gettime(CLOCK_PROCESS_CPUTIME_ID)&quot;` is the</span></div>
<div class="line"><a id="l00105" name="l00105"></a><span class="lineno">  105</span><span class="comment">   * underlying native mechanism as of this writing.</span></div>
<div class="line"><a id="l00106" name="l00106"></a><span class="lineno">  106</span><span class="comment">   *</span></div>
<div class="line"><a id="l00107" name="l00107"></a><span class="lineno">  107</span><span class="comment">   * ### Obervations, informal suggestions ###</span></div>
<div class="line"><a id="l00108" name="l00108"></a><span class="lineno">  108</span><span class="comment">   * Firstly see `S_REAL_HI_RES` and ensure that one isn&#39;t sufficient for your needs, as it is much more accurate and</span></div>
<div class="line"><a id="l00109" name="l00109"></a><span class="lineno">  109</span><span class="comment">   * computationally cheaper by 1-2 orders of magnitude based on our observations in Mac and Linux runs.</span></div>
<div class="line"><a id="l00110" name="l00110"></a><span class="lineno">  110</span><span class="comment">   *</span></div>
<div class="line"><a id="l00111" name="l00111"></a><span class="lineno">  111</span><span class="comment">   * Processor time actually measures processor *cycles* being spent to make computations.  (I/O ops and idle time</span></div>
<div class="line"><a id="l00112" name="l00112"></a><span class="lineno">  112</span><span class="comment">   * are not counted.)  Every cycle spent by any processor core is either charged to this process or another process;</span></div>
<div class="line"><a id="l00113" name="l00113"></a><span class="lineno">  113</span><span class="comment">   * if the former then it&#39;s counted; otherwise it isn&#39;t.  Next, the cycle count is multiplied by its standard</span></div>
<div class="line"><a id="l00114" name="l00114"></a><span class="lineno">  114</span><span class="comment">   * constant time duration (which is based directly on the clock frequency, the GHz thing).  That is the result.</span></div>
<div class="line"><a id="l00115" name="l00115"></a><span class="lineno">  115</span><span class="comment">   * Multiple threads acting concurrently would all count if present, so remember that.  Further, it is apparently</span></div>
<div class="line"><a id="l00116" name="l00116"></a><span class="lineno">  116</span><span class="comment">   * not straightforward what the system will charge to process A vs. process B.  For this reason, processor-time</span></div>
<div class="line"><a id="l00117" name="l00117"></a><span class="lineno">  117</span><span class="comment">   * results of very short operations (on the order of, like, a few system calls, say) are notoriously inconsistent:</span></div>
<div class="line"><a id="l00118" name="l00118"></a><span class="lineno">  118</span><span class="comment">   * *you should strive to measure longer operations, or operation repeated many times in a row*.  This stands in</span></div>
<div class="line"><a id="l00119" name="l00119"></a><span class="lineno">  119</span><span class="comment">   * stark contrast to `S_REAL_HI_RES` which -- concurrent processor pegging aside (can usually be avoided in test</span></div>
<div class="line"><a id="l00120" name="l00120"></a><span class="lineno">  120</span><span class="comment">   * rigs) -- tends to be both accurate and consistent.  In addition, the get-time call itself can be relatively</span></div>
<div class="line"><a id="l00121" name="l00121"></a><span class="lineno">  121</span><span class="comment">   * expensive and can affect the overall efficiency of an algorithm even as one tries to measure its different parts</span></div>
<div class="line"><a id="l00122" name="l00122"></a><span class="lineno">  122</span><span class="comment">   * (again: avoid such problems by measuring longer things).</span></div>
<div class="line"><a id="l00123" name="l00123"></a><span class="lineno">  123</span><span class="comment">   *</span></div>
<div class="line"><a id="l00124" name="l00124"></a><span class="lineno">  124</span><span class="comment">   * See also `S_CPU_THREAD_TOTAL_HI_RES` if one desires per-thread timing as opposed to per-process.</span></div>
<div class="line"><a id="l00125" name="l00125"></a><span class="lineno">  125</span><span class="comment">   */</span></div>
<div class="line"><a id="l00126" name="l00126"></a><span class="lineno">  126</span>  <a class="code hl_enumvalue" href="namespaceflow_1_1perf.html#ad61fb186191e4bb824d14601d11a2eb0ac5c54159101dbdb580f0b16a9397d6f3">S_CPU_TOTAL_HI_RES</a>,</div>
<div class="line"><a id="l00127" name="l00127"></a><span class="lineno">  127</span><span class="comment"></span> </div>
<div class="line"><a id="l00128" name="l00128"></a><span class="lineno">  128</span><span class="comment">  /**</span></div>
<div class="line"><a id="l00129" name="l00129"></a><span class="lineno">  129</span><span class="comment">   * Similar to `S_CPU_TOTAL_HI_RES` but applied to the calling thread as opposed to entire process.</span></div>
<div class="line"><a id="l00130" name="l00130"></a><span class="lineno">  130</span><span class="comment">   * In POSIX `&quot;::clock_gettime(CLOCK_THREAD_CPUTIME_ID)&quot;` is the underlying native mechanism as of this writing.</span></div>
<div class="line"><a id="l00131" name="l00131"></a><span class="lineno">  131</span><span class="comment">   *</span></div>
<div class="line"><a id="l00132" name="l00132"></a><span class="lineno">  132</span><span class="comment">   * ### Obervations, informal suggestions ###</span></div>
<div class="line"><a id="l00133" name="l00133"></a><span class="lineno">  133</span><span class="comment">   * See `S_CPU_TOTAL_HI_RES`, as those comments apply equally here but on the finer-grained level of a thread as</span></div>
<div class="line"><a id="l00134" name="l00134"></a><span class="lineno">  134</span><span class="comment">   * opposed to (potentially multi-threaded) process.  Please note that formally behavior is undefined if one</span></div>
<div class="line"><a id="l00135" name="l00135"></a><span class="lineno">  135</span><span class="comment">   * tries to form a duration from two thread-time points A and B via subtraction, if A and B were obtained from</span></div>
<div class="line"><a id="l00136" name="l00136"></a><span class="lineno">  136</span><span class="comment">   * different threads.  Informally, the domains of the two respective threads are completely unrelated, so a</span></div>
<div class="line"><a id="l00137" name="l00137"></a><span class="lineno">  137</span><span class="comment">   * difference obtained from them is meaningless and can easily be, say, negative, even though time has advanced.</span></div>
<div class="line"><a id="l00138" name="l00138"></a><span class="lineno">  138</span><span class="comment">   */</span></div>
<div class="line"><a id="l00139" name="l00139"></a><span class="lineno">  139</span>  <a class="code hl_enumvalue" href="namespaceflow_1_1perf.html#ad61fb186191e4bb824d14601d11a2eb0a93867c73fb6ef991268c0052153344c2">S_CPU_THREAD_TOTAL_HI_RES</a>,</div>
<div class="line"><a id="l00140" name="l00140"></a><span class="lineno">  140</span><span class="comment"></span> </div>
<div class="line"><a id="l00141" name="l00141"></a><span class="lineno">  141</span><span class="comment">  /**</span></div>
<div class="line"><a id="l00142" name="l00142"></a><span class="lineno">  142</span><span class="comment">   * Final, invalid clock type; its numerical value equals the number of clocks currently supported.</span></div>
<div class="line"><a id="l00143" name="l00143"></a><span class="lineno">  143</span><span class="comment">   *</span></div>
<div class="line"><a id="l00144" name="l00144"></a><span class="lineno">  144</span><span class="comment">   * @internal</span></div>
<div class="line"><a id="l00145" name="l00145"></a><span class="lineno">  145</span><span class="comment">   *</span></div>
<div class="line"><a id="l00146" name="l00146"></a><span class="lineno">  146</span><span class="comment">   * If you add or remove clock types, other places (in addition to this `enum`) to change are self-explanatory;</span></div>
<div class="line"><a id="l00147" name="l00147"></a><span class="lineno">  147</span><span class="comment">   * plus update Checkpointing_timer::real_clock_types() and nearby functions.</span></div>
<div class="line"><a id="l00148" name="l00148"></a><span class="lineno">  148</span><span class="comment">   */</span></div>
<div class="line"><a id="l00149" name="l00149"></a><span class="lineno">  149</span>  <a class="code hl_enumvalue" href="namespaceflow.html#a3938730ab4b89daf13d027a5f620e7cea6fba12db09e5bebfaa04f6372c41c2cf">S_END_SENTINEL</a></div>
<div class="line"><a id="l00150" name="l00150"></a><span class="lineno">  150</span>}; <span class="comment">// enum class Clock_type</span></div>
<div class="line"><a id="l00151" name="l00151"></a><span class="lineno">  151</span><span class="comment"></span> </div>
<div class="line"><a id="l00152" name="l00152"></a><span class="lineno">  152</span><span class="comment">/**</span></div>
<div class="line"><a id="l00153" name="l00153"></a><span class="lineno">  153</span><span class="comment"> * Short-hand for a bit-set of N bits which represents the presence or absence of each of the N possible clock types</span></div>
<div class="line"><a id="l00154" name="l00154"></a><span class="lineno">  154</span><span class="comment"> * in perf::Clock_type.  This is what we use to represent such things, as it is more compact and (we suspect) faster</span></div>
<div class="line"><a id="l00155" name="l00155"></a><span class="lineno">  155</span><span class="comment"> * in typical operations, especially &quot;is clock type T enabled?&quot;.</span></div>
<div class="line"><a id="l00156" name="l00156"></a><span class="lineno">  156</span><span class="comment"> *</span></div>
<div class="line"><a id="l00157" name="l00157"></a><span class="lineno">  157</span><span class="comment"> * If C is a `Clock_types_subset`, and T is a `Clock_type`, then bit C[size_t(T)] is `true` if and only if</span></div>
<div class="line"><a id="l00158" name="l00158"></a><span class="lineno">  158</span><span class="comment"> * T is in C.</span></div>
<div class="line"><a id="l00159" name="l00159"></a><span class="lineno">  159</span><span class="comment"> *</span></div>
<div class="line"><a id="l00160" name="l00160"></a><span class="lineno">  160</span><span class="comment"> * Potential gotcha: bit-sets are indexed right-to-left (LSB-to-MSB); so if the 0th (in `enum`) clock type</span></div>
<div class="line"><a id="l00161" name="l00161"></a><span class="lineno">  161</span><span class="comment"> * is enabled and others are disabled, then a print-out of such a Clock_types_subset would be 0...0001, not 1000...0.</span></div>
<div class="line"><a id="l00162" name="l00162"></a><span class="lineno">  162</span><span class="comment"> * So watch out when reading logs.</span></div>
<div class="line"><a id="l00163" name="l00163"></a><span class="lineno">  163</span><span class="comment"> */</span></div>
<div class="line"><a id="l00164" name="l00164"></a><span class="lineno"><a class="line" href="namespaceflow_1_1perf.html#aabd93a8a40158585ed149742d8937601">  164</a></span><span class="keyword">using </span><a class="code hl_typedef" href="namespaceflow_1_1perf.html#aabd93a8a40158585ed149742d8937601">Clock_types_subset</a> = std::bitset&lt;size_t(<a class="code hl_enumvalue" href="namespaceflow_1_1perf.html#ad61fb186191e4bb824d14601d11a2eb0a6fba12db09e5bebfaa04f6372c41c2cf">Clock_type::S_END_SENTINEL</a>)&gt;;</div>
<div class="line"><a id="l00165" name="l00165"></a><span class="lineno">  165</span> </div>
<div class="line"><a id="l00166" name="l00166"></a><span class="lineno">  166</span><span class="comment">/* Normally Duration_set and Time_pt_set would be forward-declared here in _fwd.hpp and defined in a .hpp; instead</span></div>
<div class="line"><a id="l00167" name="l00167"></a><span class="lineno">  167</span><span class="comment"> * it is simply defined here in _fwd.hpp, and there is no non-_fwd.hpp.  This is in accordance with the list of</span></div>
<div class="line"><a id="l00168" name="l00168"></a><span class="lineno">  168</span><span class="comment"> * known reasonable exceptions to the _fwd.hpp pattern; namely since these are glorified aliases for</span></div>
<div class="line"><a id="l00169" name="l00169"></a><span class="lineno">  169</span><span class="comment"> * simple array&lt;&gt;s, only made as actual `struct`s to be able to provide a small free-function API around them. */</span></div>
<div class="line"><a id="l00170" name="l00170"></a><span class="lineno">  170</span><span class="comment"></span> </div>
<div class="line"><a id="l00171" name="l00171"></a><span class="lineno">  171</span><span class="comment">/**</span></div>
<div class="line"><a id="l00172" name="l00172"></a><span class="lineno">  172</span><span class="comment"> * Convenience wrapper around an `array&lt;Duration, N&gt;`, which stores a duration for each of the N possible</span></div>
<div class="line"><a id="l00173" name="l00173"></a><span class="lineno">  173</span><span class="comment"> * clock types in perf::Clock_type.  It is a completely tight wrapper, not even adding zeroing of the array values</span></div>
<div class="line"><a id="l00174" name="l00174"></a><span class="lineno">  174</span><span class="comment"> * on construction.  It only adds convenience operations (possibly as free functions), namely some common math</span></div>
<div class="line"><a id="l00175" name="l00175"></a><span class="lineno">  175</span><span class="comment"> * (such as scaling all N values by some numeric factor) and stream I/O.</span></div>
<div class="line"><a id="l00176" name="l00176"></a><span class="lineno">  176</span><span class="comment"> *</span></div>
<div class="line"><a id="l00177" name="l00177"></a><span class="lineno">  177</span><span class="comment"> * ### Design rationale ###</span></div>
<div class="line"><a id="l00178" name="l00178"></a><span class="lineno">  178</span><span class="comment"> * Performance is absolutely key, so this is to be identical to the underlying (and publicly accessible)</span></div>
<div class="line"><a id="l00179" name="l00179"></a><span class="lineno">  179</span><span class="comment"> * `array` in terms of data storage and operations.  I wrote this `struct` to avoid overloading things like</span></div>
<div class="line"><a id="l00180" name="l00180"></a><span class="lineno">  180</span><span class="comment"> * `operator-(a, b)` and `operator&lt;&lt;(ostream&amp;, x)`, when the underlying type of `a`, `b, `x` is</span></div>
<div class="line"><a id="l00181" name="l00181"></a><span class="lineno">  181</span><span class="comment"> * a standard `array`: we don&#39;t want to overload such operations on a general type, even if it&#39;s only in our</span></div>
<div class="line"><a id="l00182" name="l00182"></a><span class="lineno">  182</span><span class="comment"> * namespace.  Historically, the first cut simply made non-operator-overload free function versions of such things</span></div>
<div class="line"><a id="l00183" name="l00183"></a><span class="lineno">  183</span><span class="comment"> * operating directly on the `array`s.</span></div>
<div class="line"><a id="l00184" name="l00184"></a><span class="lineno">  184</span><span class="comment"> */</span></div>
<div class="line"><a id="l00185" name="l00185"></a><span class="lineno"><a class="line" href="structflow_1_1perf_1_1Duration__set.html">  185</a></span><span class="keyword">struct </span><a class="code hl_struct" href="structflow_1_1perf_1_1Duration__set.html">Duration_set</a></div>
<div class="line"><a id="l00186" name="l00186"></a><span class="lineno">  186</span>{<span class="comment"></span></div>
<div class="line"><a id="l00187" name="l00187"></a><span class="lineno">  187</span><span class="comment">  /// The underlying data, directly readable and writable by user.  NOT ZERO-INITIALIZED ON CONSTRUCTION (or ever).</span></div>
<div class="line"><a id="l00188" name="l00188"></a><span class="lineno"><a class="line" href="structflow_1_1perf_1_1Duration__set.html#ae7d89b9e16f45dc59b27092e0496ce4f">  188</a></span><span class="comment"></span>  std::array&lt;<a class="code hl_typedef" href="namespaceflow_1_1perf.html#a38e42ae0923eb23052e3a8a1e7956456">Duration</a>, size_t(<a class="code hl_enumvalue" href="namespaceflow_1_1perf.html#ad61fb186191e4bb824d14601d11a2eb0a6fba12db09e5bebfaa04f6372c41c2cf">Clock_type::S_END_SENTINEL</a>)&gt; <a class="code hl_variable" href="structflow_1_1perf_1_1Duration__set.html#ae7d89b9e16f45dc59b27092e0496ce4f">m_values</a>;</div>
<div class="line"><a id="l00189" name="l00189"></a><span class="lineno">  189</span>};</div>
<div class="line"><a id="l00190" name="l00190"></a><span class="lineno">  190</span><span class="comment"></span> </div>
<div class="line"><a id="l00191" name="l00191"></a><span class="lineno">  191</span><span class="comment">/**</span></div>
<div class="line"><a id="l00192" name="l00192"></a><span class="lineno">  192</span><span class="comment"> * Convenience wrapper around an `array&lt;Time_pt, N&gt;`, which stores a time point for each of the N possible</span></div>
<div class="line"><a id="l00193" name="l00193"></a><span class="lineno">  193</span><span class="comment"> * clock types in perf::Clock_type.  All discussion on Duration_set applies here equally.</span></div>
<div class="line"><a id="l00194" name="l00194"></a><span class="lineno">  194</span><span class="comment"> */</span></div>
<div class="line"><a id="l00195" name="l00195"></a><span class="lineno"><a class="line" href="structflow_1_1perf_1_1Time__pt__set.html">  195</a></span><span class="keyword">struct </span><a class="code hl_struct" href="structflow_1_1perf_1_1Time__pt__set.html">Time_pt_set</a></div>
<div class="line"><a id="l00196" name="l00196"></a><span class="lineno">  196</span>{<span class="comment"></span></div>
<div class="line"><a id="l00197" name="l00197"></a><span class="lineno">  197</span><span class="comment">  /// The underlying data, directly readable and writable by user.  NOT ZERO-INITIALIZED ON CONSTRUCTION (or ever).</span></div>
<div class="line"><a id="l00198" name="l00198"></a><span class="lineno"><a class="line" href="structflow_1_1perf_1_1Time__pt__set.html#a9867f05832f22c6aceb340c0ba697dbc">  198</a></span><span class="comment"></span>  std::array&lt;<a class="code hl_typedef" href="namespaceflow_1_1perf.html#ace5f154155a7d9d5c112c1a83aa04fb5">Time_pt</a>, size_t(<a class="code hl_enumvalue" href="namespaceflow_1_1perf.html#ad61fb186191e4bb824d14601d11a2eb0a6fba12db09e5bebfaa04f6372c41c2cf">Clock_type::S_END_SENTINEL</a>)&gt; <a class="code hl_variable" href="structflow_1_1perf_1_1Time__pt__set.html#a9867f05832f22c6aceb340c0ba697dbc">m_values</a>;</div>
<div class="line"><a id="l00199" name="l00199"></a><span class="lineno">  199</span>};</div>
<div class="line"><a id="l00200" name="l00200"></a><span class="lineno">  200</span> </div>
<div class="line"><a id="l00201" name="l00201"></a><span class="lineno">  201</span><span class="comment">// Free functions.</span></div>
<div class="line"><a id="l00202" name="l00202"></a><span class="lineno">  202</span><span class="comment"></span> </div>
<div class="line"><a id="l00203" name="l00203"></a><span class="lineno">  203</span><span class="comment">/**</span></div>
<div class="line"><a id="l00204" name="l00204"></a><span class="lineno">  204</span><span class="comment"> * Prints string representation of the given clock type `enum` value to the given `ostream`.</span></div>
<div class="line"><a id="l00205" name="l00205"></a><span class="lineno">  205</span><span class="comment"> *</span></div>
<div class="line"><a id="l00206" name="l00206"></a><span class="lineno">  206</span><span class="comment"> * @param os</span></div>
<div class="line"><a id="l00207" name="l00207"></a><span class="lineno">  207</span><span class="comment"> *        Stream to which to write.</span></div>
<div class="line"><a id="l00208" name="l00208"></a><span class="lineno">  208</span><span class="comment"> * @param clock_type</span></div>
<div class="line"><a id="l00209" name="l00209"></a><span class="lineno">  209</span><span class="comment"> *        Object to serialize.</span></div>
<div class="line"><a id="l00210" name="l00210"></a><span class="lineno">  210</span><span class="comment"> * @return `os`.</span></div>
<div class="line"><a id="l00211" name="l00211"></a><span class="lineno">  211</span><span class="comment"> */</span></div>
<div class="line"><a id="l00212" name="l00212"></a><span class="lineno">  212</span>std::ostream&amp; <a class="code hl_function" href="namespaceflow_1_1perf.html#a5bb3a068357516df714c4266ec5c3df4">operator&lt;&lt;</a>(std::ostream&amp; os, <a class="code hl_enumeration" href="namespaceflow_1_1perf.html#ad61fb186191e4bb824d14601d11a2eb0">Clock_type</a> clock_type);</div>
<div class="line"><a id="l00213" name="l00213"></a><span class="lineno">  213</span><span class="comment"></span> </div>
<div class="line"><a id="l00214" name="l00214"></a><span class="lineno">  214</span><span class="comment">/**</span></div>
<div class="line"><a id="l00215" name="l00215"></a><span class="lineno">  215</span><span class="comment"> * Prints string representation of the given Duration_set value to the given `ostream`.</span></div>
<div class="line"><a id="l00216" name="l00216"></a><span class="lineno">  216</span><span class="comment"> *</span></div>
<div class="line"><a id="l00217" name="l00217"></a><span class="lineno">  217</span><span class="comment"> * @relatesalso Duration_set</span></div>
<div class="line"><a id="l00218" name="l00218"></a><span class="lineno">  218</span><span class="comment"> *</span></div>
<div class="line"><a id="l00219" name="l00219"></a><span class="lineno">  219</span><span class="comment"> * @param os</span></div>
<div class="line"><a id="l00220" name="l00220"></a><span class="lineno">  220</span><span class="comment"> *        Stream to which to write.</span></div>
<div class="line"><a id="l00221" name="l00221"></a><span class="lineno">  221</span><span class="comment"> * @param duration_set</span></div>
<div class="line"><a id="l00222" name="l00222"></a><span class="lineno">  222</span><span class="comment"> *        Object to serialize.</span></div>
<div class="line"><a id="l00223" name="l00223"></a><span class="lineno">  223</span><span class="comment"> * @return `os`.</span></div>
<div class="line"><a id="l00224" name="l00224"></a><span class="lineno">  224</span><span class="comment"> */</span></div>
<div class="line"><a id="l00225" name="l00225"></a><span class="lineno">  225</span>std::ostream&amp; <a class="code hl_function" href="namespaceflow_1_1perf.html#a5bb3a068357516df714c4266ec5c3df4">operator&lt;&lt;</a>(std::ostream&amp; os, <span class="keyword">const</span> <a class="code hl_struct" href="structflow_1_1perf_1_1Duration__set.html">Duration_set</a>&amp; duration_set);</div>
<div class="line"><a id="l00226" name="l00226"></a><span class="lineno">  226</span><span class="comment"></span> </div>
<div class="line"><a id="l00227" name="l00227"></a><span class="lineno">  227</span><span class="comment">/**</span></div>
<div class="line"><a id="l00228" name="l00228"></a><span class="lineno">  228</span><span class="comment"> * Advances each `Duration` in the target Duration_set by the given respective addend `Duration`s (negative Duration</span></div>
<div class="line"><a id="l00229" name="l00229"></a><span class="lineno">  229</span><span class="comment"> * causes advancing backwards).</span></div>
<div class="line"><a id="l00230" name="l00230"></a><span class="lineno">  230</span><span class="comment"> *</span></div>
<div class="line"><a id="l00231" name="l00231"></a><span class="lineno">  231</span><span class="comment"> * @relatesalso Duration_set</span></div>
<div class="line"><a id="l00232" name="l00232"></a><span class="lineno">  232</span><span class="comment"> *</span></div>
<div class="line"><a id="l00233" name="l00233"></a><span class="lineno">  233</span><span class="comment"> * @param target</span></div>
<div class="line"><a id="l00234" name="l00234"></a><span class="lineno">  234</span><span class="comment"> *        The set of `Duration`s each of which may be modified.</span></div>
<div class="line"><a id="l00235" name="l00235"></a><span class="lineno">  235</span><span class="comment"> * @param to_add</span></div>
<div class="line"><a id="l00236" name="l00236"></a><span class="lineno">  236</span><span class="comment"> *        The set of `Duration`s each of which is added to a `target` `Duration`.</span></div>
<div class="line"><a id="l00237" name="l00237"></a><span class="lineno">  237</span><span class="comment"> * @return Reference to mutable `target` to enable standard `+=` semantics.</span></div>
<div class="line"><a id="l00238" name="l00238"></a><span class="lineno">  238</span><span class="comment"> */</span></div>
<div class="line"><a id="l00239" name="l00239"></a><span class="lineno">  239</span><a class="code hl_struct" href="structflow_1_1perf_1_1Duration__set.html">Duration_set</a>&amp; <a class="code hl_function" href="namespaceflow_1_1perf.html#a1c1e96770f8264d938ac09546a7cdb95">operator+=</a>(<a class="code hl_struct" href="structflow_1_1perf_1_1Duration__set.html">Duration_set</a>&amp; target, <span class="keyword">const</span> <a class="code hl_struct" href="structflow_1_1perf_1_1Duration__set.html">Duration_set</a>&amp; to_add);</div>
<div class="line"><a id="l00240" name="l00240"></a><span class="lineno">  240</span><span class="comment"></span> </div>
<div class="line"><a id="l00241" name="l00241"></a><span class="lineno">  241</span><span class="comment">/**</span></div>
<div class="line"><a id="l00242" name="l00242"></a><span class="lineno">  242</span><span class="comment"> * Scales each `Duration` in the target Duration_set by the given numerical constant.</span></div>
<div class="line"><a id="l00243" name="l00243"></a><span class="lineno">  243</span><span class="comment"> *</span></div>
<div class="line"><a id="l00244" name="l00244"></a><span class="lineno">  244</span><span class="comment"> * @note If you plan to use division as well, always first multiply, then divide, to avoid rounding errors</span></div>
<div class="line"><a id="l00245" name="l00245"></a><span class="lineno">  245</span><span class="comment"> *       (assuming overflow is not a possibility).</span></div>
<div class="line"><a id="l00246" name="l00246"></a><span class="lineno">  246</span><span class="comment"> *</span></div>
<div class="line"><a id="l00247" name="l00247"></a><span class="lineno">  247</span><span class="comment"> * @todo Maybe allow `operator*=(Duration_set)` by a potentially negative number; same for division.</span></div>
<div class="line"><a id="l00248" name="l00248"></a><span class="lineno">  248</span><span class="comment"> *</span></div>
<div class="line"><a id="l00249" name="l00249"></a><span class="lineno">  249</span><span class="comment"> * @relatesalso Duration_set</span></div>
<div class="line"><a id="l00250" name="l00250"></a><span class="lineno">  250</span><span class="comment"> *</span></div>
<div class="line"><a id="l00251" name="l00251"></a><span class="lineno">  251</span><span class="comment"> * @param target</span></div>
<div class="line"><a id="l00252" name="l00252"></a><span class="lineno">  252</span><span class="comment"> *        The set of `Duration`s each of which may be modified.</span></div>
<div class="line"><a id="l00253" name="l00253"></a><span class="lineno">  253</span><span class="comment"> * @param mult_scale</span></div>
<div class="line"><a id="l00254" name="l00254"></a><span class="lineno">  254</span><span class="comment"> *        Constant by which to multiply each `target` `Duration`.</span></div>
<div class="line"><a id="l00255" name="l00255"></a><span class="lineno">  255</span><span class="comment"> * @return Reference to mutable `target` to enable standard `*=` semantics.</span></div>
<div class="line"><a id="l00256" name="l00256"></a><span class="lineno">  256</span><span class="comment"> */</span></div>
<div class="line"><a id="l00257" name="l00257"></a><span class="lineno">  257</span><a class="code hl_struct" href="structflow_1_1perf_1_1Duration__set.html">Duration_set</a>&amp; <a class="code hl_function" href="namespaceflow_1_1perf.html#a129032bde1082e8f2681669acf6bf03d">operator*=</a>(<a class="code hl_struct" href="structflow_1_1perf_1_1Duration__set.html">Duration_set</a>&amp; target, uint64_t mult_scale);</div>
<div class="line"><a id="l00258" name="l00258"></a><span class="lineno">  258</span><span class="comment"></span> </div>
<div class="line"><a id="l00259" name="l00259"></a><span class="lineno">  259</span><span class="comment">/**</span></div>
<div class="line"><a id="l00260" name="l00260"></a><span class="lineno">  260</span><span class="comment"> * Divides each `Duration` in the target Duration_set by the given numerical constant.</span></div>
<div class="line"><a id="l00261" name="l00261"></a><span class="lineno">  261</span><span class="comment"> *</span></div>
<div class="line"><a id="l00262" name="l00262"></a><span class="lineno">  262</span><span class="comment"> * @note If you plan to user multiplication as well, always first multiply, then divide, to avoid rounding errors</span></div>
<div class="line"><a id="l00263" name="l00263"></a><span class="lineno">  263</span><span class="comment"> *       (and assuming overflow is not a possibility).</span></div>
<div class="line"><a id="l00264" name="l00264"></a><span class="lineno">  264</span><span class="comment"> *</span></div>
<div class="line"><a id="l00265" name="l00265"></a><span class="lineno">  265</span><span class="comment"> * @relatesalso Duration_set</span></div>
<div class="line"><a id="l00266" name="l00266"></a><span class="lineno">  266</span><span class="comment"> *</span></div>
<div class="line"><a id="l00267" name="l00267"></a><span class="lineno">  267</span><span class="comment"> * @param target</span></div>
<div class="line"><a id="l00268" name="l00268"></a><span class="lineno">  268</span><span class="comment"> *        The set of `Duration`s each of which may be modified.</span></div>
<div class="line"><a id="l00269" name="l00269"></a><span class="lineno">  269</span><span class="comment"> * @param div_scale</span></div>
<div class="line"><a id="l00270" name="l00270"></a><span class="lineno">  270</span><span class="comment"> *        Constant by which to divide each `target` `Duration`.</span></div>
<div class="line"><a id="l00271" name="l00271"></a><span class="lineno">  271</span><span class="comment"> * @return Reference to mutable `target` to enable standard `/=` semantics.</span></div>
<div class="line"><a id="l00272" name="l00272"></a><span class="lineno">  272</span><span class="comment"> */</span></div>
<div class="line"><a id="l00273" name="l00273"></a><span class="lineno">  273</span><a class="code hl_struct" href="structflow_1_1perf_1_1Duration__set.html">Duration_set</a>&amp; <a class="code hl_function" href="namespaceflow_1_1perf.html#aff603762f38b9e3e3d50b833e09c3f91">operator/=</a>(<a class="code hl_struct" href="structflow_1_1perf_1_1Duration__set.html">Duration_set</a>&amp; target, uint64_t div_scale);</div>
<div class="line"><a id="l00274" name="l00274"></a><span class="lineno">  274</span><span class="comment"></span> </div>
<div class="line"><a id="l00275" name="l00275"></a><span class="lineno">  275</span><span class="comment">/**</span></div>
<div class="line"><a id="l00276" name="l00276"></a><span class="lineno">  276</span><span class="comment"> * Returns a Duration_set representing the time that passed since `from` to `to` (negative if `to` happened earlier),</span></div>
<div class="line"><a id="l00277" name="l00277"></a><span class="lineno">  277</span><span class="comment"> * for each `Clock_type` stored.</span></div>
<div class="line"><a id="l00278" name="l00278"></a><span class="lineno">  278</span><span class="comment"> *</span></div>
<div class="line"><a id="l00279" name="l00279"></a><span class="lineno">  279</span><span class="comment"> * @relatesalso Time_pt_set</span></div>
<div class="line"><a id="l00280" name="l00280"></a><span class="lineno">  280</span><span class="comment"> *</span></div>
<div class="line"><a id="l00281" name="l00281"></a><span class="lineno">  281</span><span class="comment"> * @param to</span></div>
<div class="line"><a id="l00282" name="l00282"></a><span class="lineno">  282</span><span class="comment"> *        The minuend set of time points.</span></div>
<div class="line"><a id="l00283" name="l00283"></a><span class="lineno">  283</span><span class="comment"> * @param from</span></div>
<div class="line"><a id="l00284" name="l00284"></a><span class="lineno">  284</span><span class="comment"> *        The subtrahend set of time points.</span></div>
<div class="line"><a id="l00285" name="l00285"></a><span class="lineno">  285</span><span class="comment"> * @return See above.</span></div>
<div class="line"><a id="l00286" name="l00286"></a><span class="lineno">  286</span><span class="comment"> */</span></div>
<div class="line"><a id="l00287" name="l00287"></a><span class="lineno">  287</span><a class="code hl_struct" href="structflow_1_1perf_1_1Duration__set.html">Duration_set</a> <a class="code hl_function" href="namespaceflow_1_1perf.html#af4b93cb0638c3d0bcfcf36903f0a3e46">operator-</a>(<span class="keyword">const</span> <a class="code hl_struct" href="structflow_1_1perf_1_1Time__pt__set.html">Time_pt_set</a>&amp; to, <span class="keyword">const</span> <a class="code hl_struct" href="structflow_1_1perf_1_1Time__pt__set.html">Time_pt_set</a>&amp; from);</div>
<div class="line"><a id="l00288" name="l00288"></a><span class="lineno">  288</span><span class="comment"></span> </div>
<div class="line"><a id="l00289" name="l00289"></a><span class="lineno">  289</span><span class="comment">/**</span></div>
<div class="line"><a id="l00290" name="l00290"></a><span class="lineno">  290</span><span class="comment"> * Advances each `Time_pt` in the target Time_pt_set by the given respective addend `Duration`s (negative `Duration`</span></div>
<div class="line"><a id="l00291" name="l00291"></a><span class="lineno">  291</span><span class="comment"> * causes advancing backwards).</span></div>
<div class="line"><a id="l00292" name="l00292"></a><span class="lineno">  292</span><span class="comment"> *</span></div>
<div class="line"><a id="l00293" name="l00293"></a><span class="lineno">  293</span><span class="comment"> * @param target</span></div>
<div class="line"><a id="l00294" name="l00294"></a><span class="lineno">  294</span><span class="comment"> *        The set of `Time_pt`s each of which may be modified.</span></div>
<div class="line"><a id="l00295" name="l00295"></a><span class="lineno">  295</span><span class="comment"> * @param to_add</span></div>
<div class="line"><a id="l00296" name="l00296"></a><span class="lineno">  296</span><span class="comment"> *        The set of `Duration`s each of which is added to a `target` `Time_pt`.</span></div>
<div class="line"><a id="l00297" name="l00297"></a><span class="lineno">  297</span><span class="comment"> * @return Reference to mutable `target` to enable standard `+=` semantics.</span></div>
<div class="line"><a id="l00298" name="l00298"></a><span class="lineno">  298</span><span class="comment"> */</span></div>
<div class="line"><a id="l00299" name="l00299"></a><span class="lineno">  299</span><a class="code hl_struct" href="structflow_1_1perf_1_1Time__pt__set.html">Time_pt_set</a>&amp; <a class="code hl_function" href="namespaceflow_1_1perf.html#a1c1e96770f8264d938ac09546a7cdb95">operator+=</a>(<a class="code hl_struct" href="structflow_1_1perf_1_1Time__pt__set.html">Time_pt_set</a>&amp; target, <span class="keyword">const</span> <a class="code hl_struct" href="structflow_1_1perf_1_1Duration__set.html">Duration_set</a>&amp; to_add);</div>
<div class="line"><a id="l00300" name="l00300"></a><span class="lineno">  300</span> </div>
<div class="line"><a id="l00301" name="l00301"></a><span class="lineno">  301</span>} <span class="comment">// namespace flow::perf</span></div>
<div class="ttc" id="acommon_8hpp_html"><div class="ttname"><a href="common_8hpp.html">common.hpp</a></div></div>
<div class="ttc" id="anamespaceflow_1_1perf_html"><div class="ttname"><a href="namespaceflow_1_1perf.html">flow::perf</a></div><div class="ttdoc">Flow module containing tools for profiling and optimization.</div><div class="ttdef"><b>Definition:</b> <a href="checkpt__timer_8cpp_source.html#l00024">checkpt_timer.cpp:25</a></div></div>
<div class="ttc" id="anamespaceflow_1_1perf_html_a129032bde1082e8f2681669acf6bf03d"><div class="ttname"><a href="namespaceflow_1_1perf.html#a129032bde1082e8f2681669acf6bf03d">flow::perf::operator*=</a></div><div class="ttdeci">Duration_set &amp; operator*=(Duration_set &amp;target, uint64_t mult_scale)</div><div class="ttdoc">Scales each Duration in the target Duration_set by the given numerical constant.</div><div class="ttdef"><b>Definition:</b> <a href="clock__type_8cpp_source.html#l00058">clock_type.cpp:58</a></div></div>
<div class="ttc" id="anamespaceflow_1_1perf_html_a1c1e96770f8264d938ac09546a7cdb95"><div class="ttname"><a href="namespaceflow_1_1perf.html#a1c1e96770f8264d938ac09546a7cdb95">flow::perf::operator+=</a></div><div class="ttdeci">Duration_set &amp; operator+=(Duration_set &amp;target, const Duration_set &amp;to_add)</div><div class="ttdoc">Advances each Duration in the target Duration_set by the given respective addend Durations (negative ...</div><div class="ttdef"><b>Definition:</b> <a href="clock__type_8cpp_source.html#l00038">clock_type.cpp:38</a></div></div>
<div class="ttc" id="anamespaceflow_1_1perf_html_a38e42ae0923eb23052e3a8a1e7956456"><div class="ttname"><a href="namespaceflow_1_1perf.html#a38e42ae0923eb23052e3a8a1e7956456">flow::perf::Duration</a></div><div class="ttdeci">Fine_duration Duration</div><div class="ttdoc">Short-hand for a high-precision boost.chrono duration, formally equivalent to flow::Fine_duration.</div><div class="ttdef"><b>Definition:</b> <a href="clock__type__fwd_8hpp_source.html#l00039">clock_type_fwd.hpp:39</a></div></div>
<div class="ttc" id="anamespaceflow_1_1perf_html_a5bb3a068357516df714c4266ec5c3df4"><div class="ttname"><a href="namespaceflow_1_1perf.html#a5bb3a068357516df714c4266ec5c3df4">flow::perf::operator&lt;&lt;</a></div><div class="ttdeci">std::ostream &amp; operator&lt;&lt;(std::ostream &amp;os, const Checkpointing_timer::Checkpoint &amp;checkpoint)</div><div class="ttdoc">Prints string representation of the given Checkpoint to the given ostream.</div><div class="ttdef"><b>Definition:</b> <a href="checkpt__timer_8cpp_source.html#l00335">checkpt_timer.cpp:335</a></div></div>
<div class="ttc" id="anamespaceflow_1_1perf_html_a75b06c669e720c60621f3c68c3d34408"><div class="ttname"><a href="namespaceflow_1_1perf.html#a75b06c669e720c60621f3c68c3d34408">flow::perf::duration_rep_t</a></div><div class="ttdeci">Duration::rep duration_rep_t</div><div class="ttdoc">The raw type used in Duration to store its clock ticks.</div><div class="ttdef"><b>Definition:</b> <a href="clock__type__fwd_8hpp_source.html#l00050">clock_type_fwd.hpp:50</a></div></div>
<div class="ttc" id="anamespaceflow_1_1perf_html_aabd93a8a40158585ed149742d8937601"><div class="ttname"><a href="namespaceflow_1_1perf.html#aabd93a8a40158585ed149742d8937601">flow::perf::Clock_types_subset</a></div><div class="ttdeci">std::bitset&lt; size_t(Clock_type::S_END_SENTINEL)&gt; Clock_types_subset</div><div class="ttdoc">Short-hand for a bit-set of N bits which represents the presence or absence of each of the N possible...</div><div class="ttdef"><b>Definition:</b> <a href="clock__type__fwd_8hpp_source.html#l00164">clock_type_fwd.hpp:164</a></div></div>
<div class="ttc" id="anamespaceflow_1_1perf_html_ace5f154155a7d9d5c112c1a83aa04fb5"><div class="ttname"><a href="namespaceflow_1_1perf.html#ace5f154155a7d9d5c112c1a83aa04fb5">flow::perf::Time_pt</a></div><div class="ttdeci">Fine_time_pt Time_pt</div><div class="ttdoc">Short-hand for a high-precision boost.chrono point in time, formally equivalent to flow::Fine_time_pt...</div><div class="ttdef"><b>Definition:</b> <a href="clock__type__fwd_8hpp_source.html#l00033">clock_type_fwd.hpp:33</a></div></div>
<div class="ttc" id="anamespaceflow_1_1perf_html_ad61fb186191e4bb824d14601d11a2eb0"><div class="ttname"><a href="namespaceflow_1_1perf.html#ad61fb186191e4bb824d14601d11a2eb0">flow::perf::Clock_type</a></div><div class="ttdeci">Clock_type</div><div class="ttdoc">Clock types supported by flow::perf module facilities, perf::Checkpointing_timer in particular.</div><div class="ttdef"><b>Definition:</b> <a href="clock__type__fwd_8hpp_source.html#l00066">clock_type_fwd.hpp:67</a></div></div>
<div class="ttc" id="anamespaceflow_1_1perf_html_ad61fb186191e4bb824d14601d11a2eb0a1490431155a134162390180995550ca7"><div class="ttname"><a href="namespaceflow_1_1perf.html#ad61fb186191e4bb824d14601d11a2eb0a1490431155a134162390180995550ca7">flow::perf::Clock_type::S_CPU_SYS_LO_RES</a></div><div class="ttdeci">@ S_CPU_SYS_LO_RES</div><div class="ttdoc">Counterpart of S_CPU_USER_LO_RES, measuring processor time (kernel-level) spent by the current proces...</div></div>
<div class="ttc" id="anamespaceflow_1_1perf_html_ad61fb186191e4bb824d14601d11a2eb0a6fba12db09e5bebfaa04f6372c41c2cf"><div class="ttname"><a href="namespaceflow_1_1perf.html#ad61fb186191e4bb824d14601d11a2eb0a6fba12db09e5bebfaa04f6372c41c2cf">flow::perf::Clock_type::S_END_SENTINEL</a></div><div class="ttdeci">@ S_END_SENTINEL</div><div class="ttdoc">Final, invalid clock type; its numerical value equals the number of clocks currently supported.</div></div>
<div class="ttc" id="anamespaceflow_1_1perf_html_ad61fb186191e4bb824d14601d11a2eb0a8cbf506eda585c026dfb5b72c402d342"><div class="ttname"><a href="namespaceflow_1_1perf.html#ad61fb186191e4bb824d14601d11a2eb0a8cbf506eda585c026dfb5b72c402d342">flow::perf::Clock_type::S_REAL_HI_RES</a></div><div class="ttdeci">@ S_REAL_HI_RES</div><div class="ttdoc">Measures real time (not processor time), using the highest-resolution system clock available that gua...</div></div>
<div class="ttc" id="anamespaceflow_1_1perf_html_ad61fb186191e4bb824d14601d11a2eb0a93867c73fb6ef991268c0052153344c2"><div class="ttname"><a href="namespaceflow_1_1perf.html#ad61fb186191e4bb824d14601d11a2eb0a93867c73fb6ef991268c0052153344c2">flow::perf::Clock_type::S_CPU_THREAD_TOTAL_HI_RES</a></div><div class="ttdeci">@ S_CPU_THREAD_TOTAL_HI_RES</div><div class="ttdoc">Similar to S_CPU_TOTAL_HI_RES but applied to the calling thread as opposed to entire process.</div></div>
<div class="ttc" id="anamespaceflow_1_1perf_html_ad61fb186191e4bb824d14601d11a2eb0ac5c54159101dbdb580f0b16a9397d6f3"><div class="ttname"><a href="namespaceflow_1_1perf.html#ad61fb186191e4bb824d14601d11a2eb0ac5c54159101dbdb580f0b16a9397d6f3">flow::perf::Clock_type::S_CPU_TOTAL_HI_RES</a></div><div class="ttdeci">@ S_CPU_TOTAL_HI_RES</div><div class="ttdoc">Measures processor time (user- and kernel-level total) spent by the current process; this is the high...</div></div>
<div class="ttc" id="anamespaceflow_1_1perf_html_ad61fb186191e4bb824d14601d11a2eb0ae06b569eb44aff6a567186f4eddb12ed"><div class="ttname"><a href="namespaceflow_1_1perf.html#ad61fb186191e4bb824d14601d11a2eb0ae06b569eb44aff6a567186f4eddb12ed">flow::perf::Clock_type::S_CPU_USER_LO_RES</a></div><div class="ttdeci">@ S_CPU_USER_LO_RES</div><div class="ttdoc">Along with S_CPU_SYS_LO_RES, measures processor time (user-level) spent by the current process; this ...</div></div>
<div class="ttc" id="anamespaceflow_1_1perf_html_af4b93cb0638c3d0bcfcf36903f0a3e46"><div class="ttname"><a href="namespaceflow_1_1perf.html#af4b93cb0638c3d0bcfcf36903f0a3e46">flow::perf::operator-</a></div><div class="ttdeci">Duration_set operator-(const Time_pt_set &amp;to, const Time_pt_set &amp;from)</div><div class="ttdoc">Returns a Duration_set representing the time that passed since from to to (negative if to happened ea...</div><div class="ttdef"><b>Definition:</b> <a href="clock__type_8cpp_source.html#l00026">clock_type.cpp:26</a></div></div>
<div class="ttc" id="anamespaceflow_1_1perf_html_aff603762f38b9e3e3d50b833e09c3f91"><div class="ttname"><a href="namespaceflow_1_1perf.html#aff603762f38b9e3e3d50b833e09c3f91">flow::perf::operator/=</a></div><div class="ttdeci">Duration_set &amp; operator/=(Duration_set &amp;target, uint64_t div_scale)</div><div class="ttdoc">Divides each Duration in the target Duration_set by the given numerical constant.</div><div class="ttdef"><b>Definition:</b> <a href="clock__type_8cpp_source.html#l00068">clock_type.cpp:68</a></div></div>
<div class="ttc" id="anamespaceflow_html_a3938730ab4b89daf13d027a5f620e7cea6fba12db09e5bebfaa04f6372c41c2cf"><div class="ttname"><a href="namespaceflow.html#a3938730ab4b89daf13d027a5f620e7cea6fba12db09e5bebfaa04f6372c41c2cf">flow::Flow_log_component::S_END_SENTINEL</a></div><div class="ttdeci">@ S_END_SENTINEL</div><div class="ttdoc">CAUTION – see flow::Flow_log_component doc header for directions to find actual members of this enum ...</div></div>
<div class="ttc" id="anamespaceflow_html_a48799f1263cdeedec125be51a3db2b79"><div class="ttname"><a href="namespaceflow.html#a48799f1263cdeedec125be51a3db2b79">flow::Fine_duration</a></div><div class="ttdeci">Fine_clock::duration Fine_duration</div><div class="ttdoc">A high-res time duration as computed from two Fine_time_pts.</div><div class="ttdef"><b>Definition:</b> <a href="common_8hpp_source.html#l00416">common.hpp:416</a></div></div>
<div class="ttc" id="anamespaceflow_html_a9d9cc2eeb10d398cff5591d446b763b8"><div class="ttname"><a href="namespaceflow.html#a9d9cc2eeb10d398cff5591d446b763b8">flow::Fine_time_pt</a></div><div class="ttdeci">Fine_clock::time_point Fine_time_pt</div><div class="ttdoc">A high-res time point as returned by Fine_clock::now() and suitable for precise time math in general.</div><div class="ttdef"><b>Definition:</b> <a href="common_8hpp_source.html#l00413">common.hpp:413</a></div></div>
<div class="ttc" id="astructflow_1_1perf_1_1Duration__set_html"><div class="ttname"><a href="structflow_1_1perf_1_1Duration__set.html">flow::perf::Duration_set</a></div><div class="ttdoc">Convenience wrapper around an array&lt;Duration, N&gt;, which stores a duration for each of the N possible ...</div><div class="ttdef"><b>Definition:</b> <a href="clock__type__fwd_8hpp_source.html#l00185">clock_type_fwd.hpp:186</a></div></div>
<div class="ttc" id="astructflow_1_1perf_1_1Duration__set_html_ae7d89b9e16f45dc59b27092e0496ce4f"><div class="ttname"><a href="structflow_1_1perf_1_1Duration__set.html#ae7d89b9e16f45dc59b27092e0496ce4f">flow::perf::Duration_set::m_values</a></div><div class="ttdeci">std::array&lt; Duration, size_t(Clock_type::S_END_SENTINEL)&gt; m_values</div><div class="ttdoc">The underlying data, directly readable and writable by user. NOT ZERO-INITIALIZED ON CONSTRUCTION (or...</div><div class="ttdef"><b>Definition:</b> <a href="clock__type__fwd_8hpp_source.html#l00188">clock_type_fwd.hpp:188</a></div></div>
<div class="ttc" id="astructflow_1_1perf_1_1Time__pt__set_html"><div class="ttname"><a href="structflow_1_1perf_1_1Time__pt__set.html">flow::perf::Time_pt_set</a></div><div class="ttdoc">Convenience wrapper around an array&lt;Time_pt, N&gt;, which stores a time point for each of the N possible...</div><div class="ttdef"><b>Definition:</b> <a href="clock__type__fwd_8hpp_source.html#l00195">clock_type_fwd.hpp:196</a></div></div>
<div class="ttc" id="astructflow_1_1perf_1_1Time__pt__set_html_a9867f05832f22c6aceb340c0ba697dbc"><div class="ttname"><a href="structflow_1_1perf_1_1Time__pt__set.html#a9867f05832f22c6aceb340c0ba697dbc">flow::perf::Time_pt_set::m_values</a></div><div class="ttdeci">std::array&lt; Time_pt, size_t(Clock_type::S_END_SENTINEL)&gt; m_values</div><div class="ttdoc">The underlying data, directly readable and writable by user. NOT ZERO-INITIALIZED ON CONSTRUCTION (or...</div><div class="ttdef"><b>Definition:</b> <a href="clock__type__fwd_8hpp_source.html#l00198">clock_type_fwd.hpp:198</a></div></div>
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